[mythtv-users] RAID 5 of different sized disks for mythtv storage?

Paul V. Gratz pgratz at gratz1.com
Tue Sep 12 05:37:19 UTC 2006

Awesome, thanks for all the responses! I see where I had gotten
confused when someone was talking about partitioning drives to make a
raid5 work with different sized hardware.  I didn't realize it but
they must have talking about multiple raid5's connected via LVM as
several of you commented.  

I'll make a wiki page of my experience when I get it setup.  Thanks
for the help everyone!

On Monday 11 September 2006 17:45, Tony Lill wrote:
> RAID5 is an excellent idea. Never, ever, spread a logical volume
> across multiple disks unless you have raid behind them. You're just
> asking for pain.
> A RAID5 requires the same size partitions on 3 or more disks. So if you
> stick with the 50G partitions, you can make some raid5 partitions
> using all 4 of your disks, and some more if you have space left on 3,
> and then mirror the remaining space. That will maximize your space
> while giving you redundancy.
> Maybe this ascii art will help. hda is your 250 with the other stuff,
> hdb is your 200 and hdc and hdd are your 300's. md0 and md4 are raid5
> with 3 disks, md1..md3 are raid5 with 4 disks, and md5, md6 are raid1
> (mirrored).
> hda   hdb    hdc hdd
> OS    md0-----------
> md1-----------------
> md2-----------------
> md3-----------------
> md4          md4----
>              md5----
>              md6----
> --
> Tony Lill,                         Tony.Lill at AJLC.Waterloo.ON.CA
> President, A. J. Lill Consultants        fax/data (519) 650 3571
> 539 Grand Valley Dr., Cambridge, Ont. N3H 2S2     (519) 241 2461
> --------------- http://www.ajlc.waterloo.on.ca/ ----------------
> "Welcome to All Things UNIX, where if it's not UNIX, it's CRAP!"
> "Paul V. Gratz" <pgratz at gratz1.com> writes:
> > Hey all,
> >
> >   I'm fairly early in the contemplation stage of setting up RAID for
> > my backend storage needs.  Currently I've got LVM setup across three
> > drives: part of a 250GB drive, all of a 200GB drive and all of a 300GB
> > drive.  Those drives are broken up into 50GB partitions to make it
> > easier to shift things around w/ LVM when the time comes.  I just
> > bought a new 300GB drive.
> >
> >   Setting aside the issue of each drive needing to be on its own IDE
> > bus (right now they share but I'm planning on picking up a new
> > controller card to get to one drive per bus).  Is there a way to use
> > RAID5 on 50GB partitions spread across several disks or is that asking
> > for trouble.  I think I remember someone mentioning having that kind
> > of setup.  Alternatively it sounds like I either need to get one more
> > 300GB drive or settle on 250GBs for the RAID setup wasting the last
> > 50GB of the two 300GB drives to make this work.  Is this correct?
> >
> >   I've read the two wiki pages on the subject but they don't really
> > answer my question (although it looks like they have great info on how
> > to set it up once I figure out the partitioning stuff).
> >
> > Thanks!
> > Paul
> >
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